This invention relates to a diaphragm pump for pumping slurry, and more particularly to a monitoring system for determining when the diaphragm of the pump has begun to fail.
Slurry pumps are often used with gasifiers to pump slurries of coal, coke and/or carbon into the gasifier for conversion to carbon monoxide and hydrogen. A well known slurry pump includes a flexible diaphragm that is usually formed of rubber or some other, durable, flexible material. The diaphragm is deflected or pulsed by oil that is pressurized and depressurized in accordance with movement of a piston or plunger in the pump. Generally, a glycol-based oil is used as a working fluid for actuation of the diaphragm. The diaphragm shields the oil and the pump mechanism from a pump chamber or transfer chamber wherein slurry passes into and out of the pump.
Thus, when a slurry pump operates properly, the slurry is drawn into the pump chamber and pumped out of the pump chamber without encountering the actuating mechanism or working fluid of the pump. The pump diaphragm, due to the abrasive nature of the slurry as it moves in and out of the pump chamber, is subject to wear. Ultimately, the wearing action of the slurry on the diaphragm will cause the diaphragm to rupture, resulting in pump failure because of commingling of the slurry with the pump mechanism and the working fluid of the pump. Although gradual deterioration of the pump diaphragm is expected due to the wear imposed by the slurry movement, sudden rupture of the diaphragm can occur at unpredictable times.
A typical slurry pump often includes a visual port that is usually monitored periodically by an attendant to detect visible contamination of the oil in the pump which can indicate impending rupture of the pump diaphragm. However, visual monitoring is not a reliable means of detecting impending rupture of the pump diaphragm because slight leaks in a diaphragm at the earliest stages of diaphragm failure are generally not visually perceptible.
Once a slurry pump is rendered inoperable due to diaphragm rupture, the gasifier operation must be shut down while the slurry pump is either repaired or replaced. Any shutdown of a gasifier operation is burdensome and expensive since gasifier shutdown and start-up operations, as well as pump repair and replacement operations, are time consuming and expensive, and require immediate availability of skilled personnel.
Although rough forecasts can be made, based on statistical data, of when a diaphragm will rupture, there are no presently known means for precisely predicting the earliest stages of diaphragm breakdown before severe damage occurs to the pump mechanism. Consequently, skilled personnel are often required to monitor and maintain pump operations.
It is therefore desirable to provide a reliable method and means for detecting the earliest stages of diaphragm failure in a slurry pump so that the pump can be shut down for repairs before the diaphragm failure causes severe damage to the pump mechanism.